1. Field of the Invention
The present invention relates to the collection of hazardous, or at least potentially hazardous, fumes emitted from a process for manufacturing leaded steel.
2. Description of the Related Art
It is well known that lead is toxic. In fact, lead poisoning is one of the oldest occupational diseases in the world. Once lead enters the body, it can cause anemia, damage the kidneys, interfere with the nervous system, cause memory loss, and cause reproductive disorders and birth defects.
The manufacture of leaded steel produces copious amounts of lead-containing fumes and dust. When lead, or an alloy mix containing lead, is heated to high temperatures, such as during melting and pouring operations, fuming occurs. The resulting fumes contain significant amounts of lead. Lead-containing dust is also produced at various process components during cooling, or cleaning, such as after the production of leaded steel. Lead-containing dust is also produced during cutting of leaded steel or other post forming operations.
Lead particles or dust are sufficiently small such that once airborne, they can remain airborne for extended periods of time. This significantly increases the risk of inhalation of lead into the body. Once lead-containing dust or fumes enter the lungs, about 50% of the lead is absorbed into the bloodstream. Lead may also enter the body by ingesting food or smoking cigarettes that have been handled by lead-contaminated hands. Although a smaller proportion of lead enters the bloodstream from ingestion, i.e. only about 10%, this is still a significant proportion.
In view of these significant concerns, prior artisans have devised various fume collecting systems for use in the production of leaded steel. In U.S. Pat. No. 4,524,819, Yoshimura, recognizing the dangers associated with the emission of lead-containing fumes, described a hood utilized between a tundish containing molten leaded steel and a mold. The hood is said to prevent toxic gases and fumes from diffusing and polluting the atmosphere. Although satisfactory, this approach provides fume collection at only one point of the manufacturing process.
In U.S. Pat. No. 4,527,609 to Nugent, a continuous casting plant is disclosed. Nugent described a three stage exhaust hood that collects emissions from a portion of the process, namely that downstream of a tundish, and in and around the mold and cooling or spray chamber. Again, although satisfactory, this approach ignores fumes and dust emitted from other portions of the process.
In yet another approach, Mulesa disclosed a technique and apparatus for collecting fumes during a leaded steel strand casting operation. In U.S. Pat. No. 4,724,895, Mulesa described an exhaust hood provided between a ladle and a tundish that serves to collect fumes from the tundish when in a noncasting position such as when cooling. Mulesa also described collecting fumes emitted during a torch cutting operation in which solidified steel strands are cut into pieces and sprayed with water. Mulesa further described collecting relatively hot and dry air at a location immediately upstream of the torch cutting station. The relatively hot dry air is mixed with the cooler wet gases collected from the torch cutting area to prevent condensation of the cooler gases prior to and during a filtering operation. Again, although representing an improvement over prior art approaches to fume collection, Mulesa's technique only collects hazardous fumes from a portion of the process.
Accordingly, there remains a need for an improved technique and apparatus for collecting hazardous, or at least potentially hazardous, fumes from a continuous casting operation, particularly a leaded steel manufacturing process. Specifically, in view of the increasing awareness of the health dangers associated with the inhalation and ingestion of lead, it would be desirable to provide a comprehensive fume collection system particularly adapted for the collection of lead-containing fumes or gases emitted during the manufacture of leaded steel.
Furthermore, the collection of airflows containing hazardous fumes also presents difficulties stemming from the relatively high temperatures of the airflows. Mulesa recognized this and attempted to mix relatively low temperature collected air with higher temperature airflows to avoid problems associated with such high temperature airflows. Although satisfactory, Mulesa's technique would not be practical for a comprehensive fume collection system due to the number of airflows and variance in properties and characteristics of each airflow. Accordingly, there is a need for a relatively simple and economical system and technique for protecting against excessively hot airflows that would be collected in a comprehensive fume collection system.